The present invention relates to high-strength open cell films prepared from aqueous dispersions of block copolymers of vinyl aromatic monomers and conjugated dienes, wherein the conjugated diene block may optionally be hydrogenated. The invention also relates to a process for the preparation of such high strength open cell films.
High strength solid films prepared from dispersions of block copolymers of vinyl aromatic monomers and conjugated dienes, wherein the conjugated diene block may optionally be hydrogenated, are disclosed in commonly assigned patent applications, WO 94/15997 (equivalent to Ser. No. 170,625, filed Dec. 20, 1993) and WO 96-15189 (equivalent to co pending application Ser. No. 339,862, filed Nov. 15, 1994). The disclosed films are monolithic and are not suitable for applications wherein the rapid transport of gas or moisture through the film is required.
Accordingly, there remains a need to provide films prepared from aqueous dispersions of block copolymers having high strength properties and the ability to rapidly transport gas or moisture through the film. In addition, it would be desirable to provide a process capable of preparing strong open cell films having the ability to rapidly transport gas or moisture through the film from aqueous lattices of block copolymers that use relatively short times and mild temperature conditions for the annealing step to thereby avoid significant polymer degradation. It would be desirable to provide a process for the preparation of thin elastomeric articles having the ability to rapidly transport gas or moisture by film deposition from a block copolymer latex that avoids the use of additives. What is needed, are stable aqueous dispersions of block copolymers which form good films by deposition, wherein the films anneal rapidly at moderate temperatures and demonstrate high tensile strengths and rapid transport of gas and moisture. For many uses, thin elastomeric films must demonstrate resistance to degradation by ozone. What is needed are stable aqueous dispersions of block copolymers which form ozone-resistant films, and such ozone-resistant films.